Hello I will try to help
Does the truck have power locks?
How cold is where you are? Looking to see if is just frozen
Here is a picture of the linkage
All the mechanism for the passenger door is in the door so that will not help us. Have you tried to operate the power lock rod with your hand and then while holding the lock rod pull on the inner door rod?
Is it possible something is trapped in the latch like cloth?
I tried just about everything including your latest of pulling up on the power lock rod and operating the inside handle rod. they both operate their door connections but it seems like the door latch is just not releasing form the door post. Can I gert to the door post via the back seat side panel opening?/
There is no access to any mechanism from the rear seat panel. The striker is the only thing with the bolts only removable with the door open. Look at your drivers door for reference.
This is perplexing! THe door latch has some how damaged.
I have a Dakota here at the shop. I will be able later this evening to give you my thoughts if you like after taking the panel off of this truck